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  • Rapt in Awe

    My Journey through the Astronomical Year

    Think of this as a "companion text" to this, the main web site. Not required reading, butI hope you'll find it interesting and helpful.

Quadrantids! This year – 2012 – it’s ‘our’ turn! (And mark the date for the coming Venus transit too!)

Really special astronomical events are rare – not only because they’re – well – rare, but because they are made rarer by having all the right conditions line up for your particular location, the final one being your personal schedule and, of course, the unpredictable weather.

In 2012, however, there will be at least two such events, both of which favor the US, though the first  ( the Quadrantids meteor shower) favors the East Coast a bit more than the West Coast (which is why I say it’s “our” turn since I live on the East Coast) – and the second, a transit of Venus in June, favors the West Coast a bit more than the East Coast.

Venus Transit  – See it in 2012, or wait for more than a century

In June, you say? Tell me about it later – say May.

And I will do so then in detail – but it’s not too early to mark your calendar now and thus keep it in your personal planning. So circle June 5, 2012. What is a transit of Venus? It’s a time when we can see Venus as a black dot cross the disc of the Sun – a time when Venus is actually between us and the Sun – and it happens rarely.  There have been just seven such transits since the invention of the telescope! And – of course – be careful! You will need special equipment to observe such a transit. Never look at the sun either with your naked eye or any  binocular or telescope unless it is one especially equipped just for looking at the Sun.  Such equipment isn’t expensive, though, and if you already have a telescope, would be a good investment to consider for this event and to regularly see  sunspots. I’m sure there will be several public observation points set up for those who don’t have such a telescope.

For me these are equally exciting events to witness, but the Venus transit carries the added bonus of happening in warm weather at a reasonable hour and has a whole bunch of science history associated with it – plus it isn’t going to happen again in our lifetime – unless in the coming years we find really wondrous ways to add to lifespan. Why historical?  Because scientists a couple hundred years ago lead dangerous and adventure-filled expeditions to observe a similar transit which was seen as a sort fo Rosetta Stone that would unlock all the important numbers of the solar system, giving us all planet distances and sizes.  At that time Kepler’s wonderful laws had given them the proportions of the Solar System – but they had no specific figures to plug in and no obvious way to measure any key one, such as the distance from the Earth to the Sun.  No way except this wonderful idea of observing a transit of Venus from two widely separated places on Earth – creating a baseline for a huge triangle –  and then using relatively simple math to derive the right numbers.

In Westport I will have only a couple hours to watch a portion of the transit before the sun sets, but that’s enough if the weather is clear. Here’s a simulation created using Starry Nights Pro software, of what I expect to see. It takes about a minute. Watch the top of the Sun for the entry of the dot that represents Venus.

Ok – enough – the date to reserve for Venus and the Sun is June 5. If you’re eager now for more details, go here.

Here come the Quadrantids – I mean right now!

As for the Quadrantids, I gave a head’s up on those last month because the date is right at the beginning of the year – the night of January 3-4 – which in this case really means the early morning of January 4.  Yes, I know for most locations it’s really cold at that time – this is mostly a northern hemisphere event – and morning isn’t everyone’s cup of tea – but as meteor showers go this can be really special.

The rarely seem Quandrantids (I’ve caught them once in over half a century and not at their best) are predicted to peak around 2-3 am EST on January 4.  (For the rest of the world that’s 7-8 hours Universal time January 4, 2012. Go here to convert Universal Time to your time.) This is a shower where the peak can be spectacular – 60-200 meteors an hour– but it lasts only a couple of hours. So it’s rare to have the peak come in the early morning hours for your section of the world when the showers radiant is also at or near its highest point and when the Moon offers little or no interference.

For me in Massachusetts a fairly bright 10-day-old Moon sets at 2:55 am – weather permitting – and it will be cold, I’m sure – I’ll start watching about 2 am and plan to stick at it until about 5 am. (Earlier when the moon is still up , it will be in the opposite corner of the sky to the shower’s radiant, so won’t offer much interference for those who would prefer to start around midnight.)

These links will take you to a couple of good examples of bright Quadrantids in previous years. This is a great individual meteor and ina serie sof images shows the trail it left.This leads to a nice series of photos of last year’s Quadrantids which peaked over Europe.

Where to look

So, if you love morning, if you love cold weather, and if you love gambling –  the Quadrantid meteor shower is for you!  Even if they don’t produce many, the ones that do show can be very bright so I wouldn’t discourage those in other parts of the Northern Hemisphere from looking – they’ll just see a lot fewer than those in a lucky location.

Quadrantid radiant point as it appears at 3 am January 4 from 42° N latitude. Click image for larger version. (Chart is screen shot from Starry Night Pro.)

What’s more, the Quadrantids are known for producing fireballs – the very brightest of meteors – ones that can even outshine Venus!

So how will you know a Quadrantid when you see it. After all, on any given night there can be several random meteors. The key is to note its direction. If you’re in North America, Quadrantids will generally come from the north northwest in the early evening, from north about the time of the shower’s peak, and from the north northeast later. As with so many good showers, the time to see the most Quadrantids will be in the early morning – essentially from about 1 am January 4, 2011, on.

This chart, taken from the American Meteor Society page here, is an excellent depiction of Quadrantids (the dark, straight lines) and for me drive homes the point that while the radiant is in the Northeast, the meteors can appear anywhere in the sky – afterall, that’s what the word “radiant” sure implies.

Click image for larger version. (From the American Meteor Society website.)

Here’s good advice from the American Meteor Society on this year’s Quandrantids:

Maximum rates for this shower are difficult to predict. Most observers across North America can expect to see a maximum of 40 Quadrantids per hour on the morning of January 4th. If you are lucky it could be several times higher.

A good observing strategy for observers in North America would be to begin observations near midnight. This will allow eastern observers to catch the maximum should it arrive a bit early. Pacific observers may want to start around 2300 (11pm) on the 3rd. While rates would most likely be low for western observers, any Quadrantid activity would be in the form of earth-grazing meteors, which are long-lasting and produce long trails as they graze the upper atmosphere. Face anywhere in the north to east quadrant, with your field of view half way up in the sky. This will keep the moon at your back. Quadrantid meteors will shoot upward from the northeastern horizon until it [the radiant] gains sufficient height when it can produce meteor shooting in all directions.

Observers located in the northern hemisphere other than North American can expect to see approximately 25 Quadrantids per hour between moon set and dawn. Due to the high northern declination (celestial latitude) of the Quadrantid radiant, observers in the southern hemisphere will see very few Quadrantids. As seen from the southern hemisphere the Quadrantid radiant lies low in the north, if it clears the horizon at all before dawn.

 And why are they called Quadrantids? Other meteor showers are named for the constellation in which their radiant is located – the Perseids in Perseus, the Geminids in Gemini, etc. But who knows of a constellation named Quadran…??? Well, think Pluto! There once was a constellation named Quadrans Muralis, and that’s where they appear to radiate from. But in 1932 the International Astronomical Union cleaned up sky maps, threw out some constellations, and agreed upon official boundaries for the remaining 88. Like Pluto’s full planet status, the Quadrans Muralis is no more.

Its name is Latin for is mural quadrant and refers to an instrument that was very important to astronomy before the time of telescopes. Check out this description.

And then there’s Jupiter, Mars, Saturn – and of course, Venus!

We’ve a wonderful planet show going on this month with the actors changing  positions on the celestial stage, but Jupiter still dominant with Venus on the rise and Mars and Saturn beginning to arrive early enough to catch the night owls and give us early morning-types a real treat.

Jupiter is still high in the south and in evening twilight will rival Venus in brightness. Well, not really, but it will appear that way because Venus, beaming in the western sky, will occupy a section of sky with a much brighter background.  Venus is actually about magnitude -4 and Jupiter  magnitude -2.6. Venus will get higher in the western sky each night – Jupiter will move slowly towards it.

Mars  and Saturn are still mainly morning objects, but that is changing rapidly. Mars comes up in the evening in January – but isn’t well placed for observing until later. As the Earth overtakes Mars in its orbit the two draw closer which for the naked eye observer means Mars gets a lot brighter (doubles in the course of the month) and for the telescope observer its disc gets significantly larger making it easier to detect some features.

Saturn rises close to midnight, but doesn’t become well placed for observing until the early morning. It still makes a spectacular naked eye sight, however, looking like a natural companion to the bright guidepost star, Spica.  In fact, when I first saw this pair a few weeks ago  my initial reaction was “what the heck are the Gemni twins , Castor and Pollux, doing low in the southeast!?” But while the brightness and spacing reminded me of Castor and Pollux, I knew it was the wrong section of sky and I also could see that one – Saturn – gave off a yellowish hue while Spica is the bluest of blues.

Finding Saturn and Spica is easy – you follow the arc of the Big Dipper’s handle and that will lead you first to another bright star, Arcturus and then t0 Saturn and Spica. Observing Saturn with a telescope is now a real treat because the rings are tipped to give us an excellent view of them – something that hasn’t been the case for the past few years.

Looking behind the scenes – what the actors are really doing

Watching the planet show is like watching a play where the real action is hidden from us and what we see gives us an impression of bright stars which wander – “planet” means “wanderer” – among the “fixed” and generally dimmer stars. But lets lift up the curtain and go back stage.

The following series of images – click on each to get a much larger version – focuses on the motions of Venus between now and the June 5th transit of the Sun.  The larger image shows the western sky about 30 minutes after sunset at the start of each month. It is a screen shot from SkySafari Pro software. I have added to it a screen shot that uses the online Orrery found here to show the actual position of the inner planets as seen from a vantage point above the Sun. I love this sort of thing. It’s simply cool to stand outside, see a planet, and really be able to visualize where you are and where it is. Afterall, astronomy is largely a game of such mental gymnastics and understanding these things makes your observing experience more meaningful.

So if you study the changing Orrery view you can see how the motions of the planet all relate to what we actually see in the sky.  Draw an imaginary line from the Earth through the Sun and that line marks the difference between evening and morning. From our vantage point on earth as we rotate and approach a view of the Sun each morning we see the planets that are in our morning sky – and once we pass the Sun  – as night falls – what we see is in our evening sky. That’s why I marked an “evening” and “morning” side for each Orrery view.

With that in mind, here are the images leading up to the Venus transit for the first of each month, starting with January 1, 2012. (Be sure to click on each image for the larger version.)

Looking west,  half an hour after Sunset, January 1, 2012

Looking west, half an hour after Sunset, January 1, 2012 Click image for larger version. Prepared from SkySafari Pro screen shot.

Looking west,  half an hour after Sunset, February 1, 2012

Looking west, half an hour after Sunset, February 1, 2012 Click image for larger version. Prepared from SkySafari Pro screen shot.

Looking west,  half an hour after Sunset, March 1, 2012

Looking west, half an hour after Sunset, March 1, 2012 Click image for larger version. Prepared from SkySafari Pro screen shot.

Looking west,  half an hour after Sunset, April 1, 2012

Looking west, half an hour after Sunset, April 1, 2012 Click image for larger version. Prepared from SkySafari Pro screen shot.

Looking west,  half an hour after Sunset, May 1, 2012

Looking west, half an hour after Sunset, May 1, 2012 Click image for larger version. Prepared from SkySafari Pro screen shot.

Looking west,  at Sunset, June 1, 2012

Looking west, at Sunset, June 1, 2012 Click image for larger version. Prepared from SkySafari Pro screen shot.


One Response

  1. […] I wrote in January – So circle June 5, 2012. What is a transit of Venus? It’s a time when we can see Venus as a […]

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